A flat-type display apparatus in which images, characters, and the like are displayed with high precision in the following manner has been developed. The flat-type display apparatus comprises electron beam sources and a flat electrode unit in which a plurality of electron-beam control electrodes are layered. After being focused, modulated, and deflected by the electrode unit, electron beams are further focused by wire electrodes formed by extending a plurality of wires and then are irradiated onto a phosphor screen to cause light emission.
A conventional flat-type display apparatus will be explained with reference to FIG. 2 as follows.
A conventional flat-type display apparatus 101 comprises a back electrode 106, a plurality of linear hot cathodes 107 as electron beam sources, a flat electrode unit 108, and a grid frame 110 to which wire electrodes 109 as extended electrodes have been fixed while being extended thereon orthogonally to the linear hot electrodes 107, which are housed in a vacuum case 105. The vacuum case 105 is formed of a front case 103 having a phosphor screen 102 formed on its inner face and a rear case 104.
In this case, the electrode unit 108 comprises an extracting electrode 111, a modulating electrode 112, a horizontal deflection electrode 113, and a vertical deflection electrode 114. The respective electrodes are electrically insulated from and are fixed to one another while maintaining predetermined spaces.
In order to facilitate the following description, the coordinate axes are set as follows.
An X-axis is set in the direction in which the linear hot cathodes 107 are extended. A Y-axis is set in the direction orthogonal to the X-axis in a plane of the back electrode 106. A Z-axis is set in the normal direction from the back electrode 106 toward the phosphor screen 102.
The back electrode 106 is fixed by welding or the like to fixing stands 115 that have been fixed to the rear case 104 with low melting point solder glass or the like. Springs 116 for extending the linear hot cathodes 107 are fixed by welding or the like to bases 117 that have been fixed to the rear case 104 with low melting point solder glass or the like. The linear hot cathodes 107 are extended by the springs 116 on the phosphor screen 102 side of the back electrode 106 with a predetermined tension.
Electrode fixing metal fittings 118 have insulating films 118a formed on its phosphor screen 102 side and are placed on the back electrode 106 at the upper and lower ends in the Y-axis direction.
End metal fittings 119 are fastened to the electrode unit 108 at the left and right ends in the X-axis direction using screws or the like with insulating spacers 120 being sandwiched therebetween, which is then fixed to the electrode fixing metal fittings 118.
In the extracting electrode 111, through holes 111a are formed opposing respective linear hot cathodes 107 at predetermined spaces in the X-axis direction.
The modulating electrode 112 is formed in a bamboo-blind-like shape by placing long and narrow electrodes 112b in the Y-axis direction in the X-Y plane at suitable spaces from one another corresponding to the pitch of the through holes 11a in the X-axis direction in the extracting electrode 111. The electrodes 112b have through holes 112a at the positions opposing the rows of through holes 111a along the Y-axis in the extracting electrode 111.
The horizontal deflection electrode 113 is formed by combining comb-teeth-shaped electrodes 113a and 113b with each other at suitable spaces in the same plane (in the X-Y plane). The electrodes 113a are connected to each other at their left and/or right ends in the X-axis direction and the electrodes 113b also at their left and/or right ends in the X-axis direction. The horizontal deflection electrode 113 is placed so that the center positions of slits 113c formed between projecting parts 113ab and 113bb that are combined with each other correspond to respective positions of the through holes 111a in the extracting electrode 111.
The vertical deflection electrode 114 is formed by combining comb-teeth-shaped electrodes 114a and 114b with each other at suitable spaces in the same plane (in the X-Y plane). The electrodes 114a are connected to each other at their left and/or right ends in the X-axis direction and the electrodes 114b also at their left and/or right ends in the X-axis direction. Slits 114c are formed between the electrodes 114a and 114b in the X-axis direction at the positions corresponding to the positions of the linear hot cathodes 107.
The wire electrodes 109 are formed by extending and fixing wires 109a to the picture-frame-like grid frame 110 at the positions opposing the rows of the through holes 111a along the Y-axis in the extracting electrode 111 so as to correspond to the pitch of the through holes 111a in the X-axis direction in the extracting electrode 111.
The grid frame 110 is fixed to the end metal fittings 119 using screws or the like with insulating spacers 121 being sandwiched therebetween. In this case, the grid frame 110 and the end metal fittings 119 are fixed using screws with insulating bushings 122 being sandwiched therebetween so as to be insulated electrically from each other.
Then, the front case 103 is placed over the structure comprising members from the back electrode 106 to the wire electrodes 109 that have been placed on the rear case 104 as described above. The front case 103 and the rear case 104 are fixed to each other by heating with outgoing terminals (not shown in the figure) being sandwiched therebetween using low melting point solder glass formed at the peripheries of the front case 103 and the rear case 104, thus being sealed to obtain the vacuum case 105. Then, the inside of the vacuum case 105 is evacuated through an exhaust pipe (not shown in the figure). The exhaust pipe is then closed, thus completing the flat-type display apparatus 101.
In this case, the front case 103 is placed by positioning stripes formed in the Y-axis direction constructing the phosphor screen 102 formed on the inner face of the front case 103 relative to the wires 109a forming the wire electrodes 109 with respect to the X-axis direction.
The flat-type display apparatus 101 thus formed displays images, characters, and the like with high precision by: focusing, modulating, and deflecting electron beams 123 generated from the linear hot cathodes 107 by the extracting electrode 111, the modulating electrode 112, the horizontal deflection electrode 113, and the vertical deflection electrode 114 that form the electrode unit 108; further focusing the electron beams 123 by the wire electrodes 109; and irradiating the electron beams 123 onto the phosphor screen 102 to cause light emission.
However, in order to display images, characters, and the like with high precision excellently without causing shifts in color in the conventional flat-type display apparatus, the wire electrodes 109 and the stripes forming the phosphor screen 102 must be positioned with a precision within .+-.15 .mu.m.
In the conventional configuration, the stripes of the phosphor screen 102 formed on the inner face of the front case 103 are positioned relative to the wire electrodes 109 fixed to the rear case 104 with respect to the X-axis direction. In this stage, the wire electrodes and the stripes are positioned with a precision within .+-.10 .mu.m in the X-axis direction.
However, in a later process, the rear case 104 and the front case 103 are fixed to each other by heating with low melting point solder glass with the outgoing terminals (not shown in the figure) being sandwiched therebetween.
In this process, the gap formed between the rear case 104 and the front case 103 due to the outgoing terminals and the low melting point solder glass that has not been melted yet is reduced by heating under loading in the Z direction. Thus, the rear case 104 and the front case 103 adhere and are thus fixed. The rear case 104 and the front case 103 are bonded by heating with their positions in the X-axis and Y-axis directions to be regulated. However, when the gap is reduced, the regulated condition in the X-axis and Y-axis directions is impaired, thus frequently causing a position shift on the order of several tens of .mu.m.
Therefore, in the completed flat-type display apparatus 101, the electron beams 123 cannot be irradiated onto predetermined positions on the phosphor screen 102, thus causing shifts in color. As a result, excellent images were not obtained.